Yeast and fermentation
Baker's yeast is a fungus. Its Latin name is Saccharomyces cerevisiae, which means "sugar fungus of beer". As this would suggest, the same yeast can be used to brew beer (although brewers have developed many specialised strains specifically for this purpose, so don't try home brewing with bread yeast). Whether it is making bread or beer, yeast does the same thing: it consumes sugar and produces alcohol and carbon dioxide. The carbon dioxide forms bubbles in dough, causing it to rise, while the alcohol evaporates during baking.
Yeast is generally available in three forms: fresh yeast, a crumbly light brown block which must be kept in the refrigerator and will keep for around four days; active dried yeast, consisting of small round granules - this must be mixed with water before adding to flour; and "Easyblend" or "Fast acting" yeast, which consists of finer rod-shaped granules. I find this the most convenient and reliable form of yeast, and this will be used in all the recipes on this site. Whatever form of yeast you use, a good general rule is to use just enough to raise the dough and no more (yeast doesn't taste all that nice!).
No sugar, thanks!
You've probably read bread recipes that say something like, "mix the dry yeast with 1 teaspoon of sugar in a little tepid water and leave until it goes frothy, mix into the flour and knead, then cover with a cloth and leave to rise in a warm place for one hour". No, no, a thousand times no! Please don't make bread like this, it's easy to make bread that tastes so much better.
Firstly, there is enough natural sugar in the flour to start feeding the yeast - trust me on this, I've made hundreds of loaves without sugar and they've all risen. If you add sugar, you end up with overly sweet bread (unless you're making an enriched sweet bread like challah or tsoureki, in which case, go right ahead). Secondly, the rising stage of bread making is crucial to the flavour of the finished loaf. As well as the fermentation caused by the yeast, enzymes within the flour break down some of the starch content into simpler sugars - some of which continue to feed the yeast, while the rest is left to caramelise during baking giving bread more flavour.
The magic ingredient is (wait for it!) ...
Leaving dough in a warm place to rise or adding sugar both accelerate the rising process, leaving the flour enzymes insufficient time to do their work. So, it is vital that we allow our dough to rise slowly in a cool place before baking.
This is the golden rule of great bread: time is the most important ingredient. Of course, we can't just leave dough forever and expect the flavour to improve indefinitely - if left fermenting for too long, the gluten loses too much elasticity so the loaf will not rise properly, and bacterial action will eventually cause the dough to go off. For these reasons, we need to control our slow fermentation to balance the maximum enzyme action with the best possible rise. This is generally done using either some type of preferment, or delaying fermentation by refrigerating the dough. We will look at these techniques in more detail in the equipment and techniques section.